Page 1
[124]
The compound MF-3 was obtained as chromatographically
homogeneous yellow crystalline compound, mp.272-274o, analysed for
C27H30O16. It was cyrstallised from methanol. The purity and homogeneity
was ascertained by tlc on cellulose plate.
The compound gave positive Molisch‟s test1 and but did not reduced
fehling solution nor gave positive test with AHP2 reagent, suggesting that
the reducing group of the sugar is not free and is probably involved in
glycosidic linkage. The compound was hydrolysed with 7% H2SO4 and an
aglycone along with two sugars were obtained.
The sugars were identified as D-glucose and L-rhamnose by tlc. In
order to study the molecular size of the aglycone , glycoside was thus
subjected to systematic analysis.
AGLYCONE :
The aglycone mp 312-3140C was analysed for C15H10O7 and
responded the following colour reactions characteristic of flavonoids.
Colour Reaction:
1. The ethanolic solution of the compound gave violet colour with
aqueous solution of ferric chloride (FeCl3) indicating the
polyphenolic3 nature of compound.
Page 2
[125]
2. Aglycone did not show any colour reaction or ppt. formation, with 2,4
dinitrophenyl hydrazine reagent4 indicating the absence of unhindered
carbonyl group.
3. Alc. solution on treatment with Mg-HCl developed pink colour.
(Shinoda Flavonols)5.
4. It did not get reduced by sodium borohydrate6 indicating the absence
of flavonone skeleton.
5. It gave yellow orange solution with conc. H2SO4 suggested flavone or
flavonol skeleton7.
6. It gave positive Pews test8-9
(Zn+HCl) showed its flavonol nature.
(presence of 3-OH-group).
7. On treatment with a solution of boric acid in the presence of citric
acid in acetone gave yellow colour12-13
(presence of free 5-OH-group).
8. When alc. solution was treated with vanilline HCl, a red colour
appeared15-16
(presence of 5,7, dihydroxy system).
9. Upon exposing the chromatogram to UV light, yellow violet
fluorescence appeared41
.
10. Yellow green fluorescence developed and UV light, when the spot of
its solution was sprayed with ethanolic AlCl3 and zirconium oxy
chloride separately on a strip of filter paper14
.
Page 3
[126]
11. Positive colour reaction was observed with boric acid and sodium
acetate42
.
These reactions are characteristic of 3-hydroxy flavones (flavonols),
so the compound must have got a flavonol nucleus (I)
(I)
The compound its absorption maxima at 370 and 255 nm18-19
. The
shifting patterns of these bonds by Aluminum chloride16
(with and without
HCl) sodium acetate22
and sodium acetate/boric acid43-44
were suggestive of
a penta hydroxy flavone of flavonol type.
The IR spectrum of the compound exhibited a peak at 3310 cm-1 45
which indicates the presence of OH-grouping. The hydroxyl groups were
estimated by acetylation with acetic anhydride and pyridine, there by
showing the presence of five hydroxyl groups in the compound.
Page 4
[127]
Thus out of the seven oxygen, five are present as hydroxyls, and two
in flovone nucleus hence the compound is obviously a penta hydroxy
flovone and the structure of this could tentatively by represented as (II).
(II)
The UV spectrum of aglycone showed a maxima at 258, 304,372 nm,
which was typical for flavones and the 5-OH was identified by the
banthochromic shift (40nm) observed after addition of AlCl3/HCl to a
methanolic solution of aglycone 46
.
OH
OH
OH
OH
OH
Page 5
[128]
Spectral Studies:
Table - I
UV Spectral data of aglycone
The IR spectrum showed absorption band are 3407 cm-1
that is
characteristic of OH group 3310cm-1
. Absorption at 1665.85 cm-1
is due to
>C=O chelated. Other absorption frequencies include 1610.45, 1562, 1522
and 1453.59 as a result for ring system. The absorption frequency 1262.29
cm-1
for C-O-C- vibration and 822.70cm-1
signifies in -C-H in CH2.
Medium of Spectrum Bond position in nm
MeOH
max
258,304 sh,372,
+NaOMe 248 sh, 320d,
+AlCl3 275,304 sh,333,460
+AlCl3/HCl 265,301sh,360,430
+Na OAc 257 sh,274,330,390,
+ NaOAc/H3BO3 261,301sh,390.
Page 6
[129]
Table – II
IR spectral data of aglycone
S.N. Peak cm-1
Assignment
1 3310.58 - OH
2 1665.85 C=O (chelated)
3 1610.45,
1562.181,
1522.00
1453.59
ring system.
4 1262.29 C-O-C-vibration
5 822.70 -C-H in CH2
Page 8
[131]
1H NMR spectrum showed the presence of five aromatic protons. Two
protons were meta coupled and appeared as doublets at 6.17 (1H,d,J=2.0 Hz)
and 6.37 (1H,d,J=2.0Hz) ppm, assignable to H-6 and H-8 respectively. One
meta coupled doublet at 7.70) ppm (1H,d,J=8.0`Hz) corresponds to the H-5`
and a double doublet integrating for two protons at 7. 73 (1H,dd,J=2.0,7.5)
and 7.62 ppm (1H,d,J=2.0Hz) was attributed to the H-2` and H-6` protons.
Table – III
1H NMR chemical shifts of the aglycone ppm from TMS
(CDCl3+DMSO d6 300 MHz)
Assignments Chemical Shift ( :ppm) J-Value (Hz)
H-6 6.17 (1H,d) 2.0
H.8 6.37 2.0
H-5` 6.87 (1H,d) 8.0
H-2` 7.73 (1H,d) 2.0
H-6` 7.62 (1H,dd) 2.0,7.5
The 13
C NMR spectra revealed 15 carbon signals typical of flavonoids
nucleus. The low field signal at 176.3 ppm was due to the carbonyl group at
C-4 and C-2 (156.6) ppm was down field shifted28
.
Page 11
[134]
Table – IV
13C
NMR chemical shifts of the aglycone ppm from TMS
(CDCl3+DMSO – 300 MHz)
Assignment Chemical Shift
C-2 156.6
C-3 136.2
C-4 176.3
C-5 161.2
C-6 98.8
C-7 164.5
C-8 93.7
C-9 148.2
C-10 103.4
C-1` 120.4
C-2` 116.1
C-3` 145.5
C-4` 147.5
C-5` 115.5
C-6` 122.4
Page 14
[137]
( III)
This is finally confirmed from the 13
C NMR.
The important fragmentation pattern obtained in the electron impact
mass spectrum of the aglycone and the different species obtained during
fragmentation are shown in the (scheme-I) and were found to be in complete
accord with the structure assigned to it.
Mass : m/z 302 [M+], 301, 274, 273, 153, 152, 134, 132, 124.
Page 15
[138]
-CO
R.D.A Cleavag
e
m/z - 302
m/z - 301
m/z - 274
m/z - 273
m/z - 134
m/z - 132 m/z - 124
m/z - 152
Scheme - I
Page 17
[140]
Alkaline Degradation of the Aglycone :
The aglycone on fusion with 50% ethanolic KOH gave two
compounds identified as protocatechuic acid molecular formula C7H6O4,
mp.198-199, M+154 and phloroglucinol molecular formula C6H6O3,
mp. 117-118, M+ 126.
1H NMR spectrum of penta acetyl derivative of the aglycone:
The 1H NMR spectrum of penta acetyl derivative of the aglycone was
found to be in complete conformity with the above structure.
The significant signals obtained in 1H NMR spectrum of the penta
acetyl derivative of the aglycone and structural unit inferred with the help of
available literature47-48
are given below in the table (V).
Protocatechuic acid
Phloroglucinol
Page 18
[141]
Table – V
1H NMR chemical shifts of the penta acetyl of aglycone
ppm from TMS
S.
N.
Assignments chemical shift
( :ppm)
J-Value (Hz)
1 H-2` 7.35 (1H,d) 2.5
2 H-6` 7.65 (1H,dd) 2.5,9.0
3 H-5` 7.00 (1H,d) 9.0
4 H-6 6.50 (1H,d) 2.4
5 H-8 6.53 (1H,d) 2.0
6 OAc – 3` 2.44 (3H,s) ---
7 OAc – 4` 2.33 (3H,s) ---
8 OAc – 7 2.40(3H,s) ---
9 OAc – 5 2.39 (3H,s) ---
10 OAc - 3 2.50(3H,s) ---
Page 19
[142]
GLYCOSIDE
The glycoside C27H30O16 on hydrolysis gave the aglycone C15H10O7
and rhamnose along with glucose as sugar moieties.
C27H30O16 C15H10O7 + C6H12O5 + C6H12O6
aglycone rhamnose glucose
Quantitative sugar estimation29-30
confirmed the presence of two moles
of sugar per mole of glycoside was done by procedure of Mishra and Rao31
which indicated that the sugars were present in the ratio of 1:1. The two
sugars might be linked to two different hydroxyl groups of the aglycone as a
diglycoside or they might be attached mutually and linked to the aglycone at
one of the hydroxyl group as a bioside. Complete structural elucidation of
the compound MF-3, was determined by its chemical analysis diagnostic UV
shift 1H NMR and
13C NMR spectra.
49-50
Position of sugar linkage :
By comparing the UV spectra of aglycone and the glycoside, the
position of sugar moieties to the aglycone was fixed at position C-3, on the
basis of following points.
Page 20
[143]
1. UV absorption data and spectral shift upon addition of AlCl3 and H3BO3
indicated the presence of – OH groups at C-3` and C-4` position in the
aglycone and and glycoside.51-52
2. Banthochromic shift with AlCl3 and CH3COONa indicated the presence
of –OH groups at C-5 and C-7 in the aglycone, and the glycoside.
3. Yellow fluorescence of the aglycone in UV light and the spectral shift
with AlCl3 in presence of HCl relative to band I in MeOH suggested a
free 3-OH group in the aglycone.32
But the C-3-OH group was shown to
be absent by the UV spectrum of glycoside, as it did not show any
florescence and no shift in band I in methanol.23,25
This was further confirmed by the comparision of the glycoside and
aglycone by subjecting them to test for flavonols. In this test the glycoside
failed to respond the test for flavonols (3-hydroxyl group) where as the
aglycone does well.
As there is only one possible site available for glycosylation. Hence it
might be expedient to conclude here that the sugars are present as bioside
type and linked to the aglycone at position-353
.
Page 21
[144]
Nature of the sugar linkage:
The 1H NMR spectral shift (table –VI) of the glycoside displayed two
anomeric proton signals at 5.47 (1H,d, J=2 Hz) and 4.45, (1H,d, J=7 Hz)
ppm, these were attributed to H-1`` glucosyl and H-1``` rhamnosyl protons
respectively. A broad signal at 3.60-4.30 ppm integrating for 10 protons
corresponds to the rest of the sugar protons. The rhamnose methyl signal
appeared at 0.90 (br, J=6Hz, 3 H) ppm attributed to the (1 6) linkage
between rhamnose and glucose.
The conclusion was further confirmed by the permethylation of the
glycoside by Hakomori‟s Mehtod40
followed by hydrolysis. The partly
methylated sugar thus obtained were identified as 2,3,4, tri-o-methyl
D-glucose and 2,3,4, tri-o- methyl L- rhamnose by comparing their RG value
with 2,3,4,6 – methyl D- glucose as reference sugar (n BuOH: EtOH: H2O,
5:1:4 RG = 0. 65 and 1.02 respectively spray AHP). As the reducing group
of both the sugar was involved in glycosidic linkage, the glycoside was non
reducing in nature.
Easy hydrolysis eliminated the possibility of any C-C-type glycosidic
linkage and suggested the C-O-C type of linkage.
Page 22
[145]
Per iodate oxidation of the glycoside with all the hydroxyl group
methylated, consumed three mole of per iodate and liberated one mole of
formic acid per mole of glycoside methyl ether. From this observation it has
evident that the two sugars are present as bioside in their pyranose form.
For determining the sequence of sugars in disaccharide unit, mild acid
hydrolysis of the glycoside was carried out using 1% HCl. The course of
hydrolysis was progressively followed at regular interval of time by testing
the hydrolysate for two sugars. It was found that rhamnose made its
appearance first and it was only after some time that glucose could be
detected, there by indicating that rhamnose is the terminal sugar and glucose
is directly attached to aglycone.
Table – VI
1H NMR chemical shift of the glycoside ppm from TMS
(DMSO + CDCl3 300 MHz)
Assignments chemical shift ( :ppm) J-Value (Hz)
H-2` 7.82 (1H,d) 2.0
H-6` 7.57 (1H,dd) 2.0, 7.5
H-5` 6.85 (1H,d) 8.0
H-6 6.12 (1H,d) 2.4
Page 23
[146]
H-8 6.30 (1H,d) 2.0, Hz
H-1``-glucose 5.18 (1H,d) 7.6
H-1```-rhamnosyl 4.38 (1H,d) 2.0
Sugar protons 3.60-3.85 (4H,br,m) ---
rhamnose methyl 0.90 (2H,br,m) 6.3 Hz
rhamnose protons 3.20-3.70 (4H,m)
(2```,3```,4```,5```)
---
After assigning the sugar protons in the 1H NMR spectrum, the
aromatic protons may easily be encountered. The two upfield meta coupling
doublets at 6.12 (1H, d, J= 2.4) and 6. 30 (1H,d, J=2.0 Hz) ppm were
assignable to the H-6 and H-8 protons of ring A. The meta coupled doublet
at 6.85 (1H,d, J=8.0 Hz) were assignable to proton H-5` the doublet of
two protons at 7.82 (1H,d, J= 2.0) and 7.57 (1H,dd,2.0, 7.5 Hz) were
assigned to the H-2` and H-6` protons as they were absorbed at low field.
1H NMR spectrum of deca acetyl derivative of the glycoside:
The 1H NMR spectrums the deca acetyl derivative of the glycoside
was found to be in complete confirming with the glycoside. The significant
signals obtained in the 1H NMR spectrum of the deca acetyl derivative of the
Page 24
[147]
glycoside and the structural units inferred with the help of available
literature are given in the Table – VII
Table – VII
1H NMR chemical shifts of the deca acetyl of glycoside
ppm from TMS
S.
N. Assignments
chemical shift
( :ppm) J-Value (Hz)
1 H-2` 7.35 (1H,d) 2.5
2 H-6` 7.65 (1H,dd) 2.5,9.0
3 H-5` 7.00 (1H,d) 9.0
4 H-6 6.50 (1H,d) 2.4
5 H-8 6.53 (1H,d) 2.0
6 OAc – 3` 2.44 (3H,s) ---
7 OAc – 4` 2.33 (3H,s) ---
8 OAc – 7 2.40(3H,s) ---
9 OAc – 5 2.39 (3H,s) ---
10 H-1`` of glucose 4.32 (1H,d) 7.0
11 protons of glucosyl unit 3.5-4.30 (6H,m) ---
12 H-1``` of rhamnose 5.47 (1H,d) 2.0
13 ``rhamnose methyl 0.78 (3H,m) 6.0
14 protons of rhamnose 4.66 -5.30 (4H,m) --
15 OAc – 2`` 2.00 (3H,s) --
16 OAc – 3`` 2.00 (3H,s) --
17 OAc – 4`` 1.94 (3H,s) --
18 OAc – 2``` 2.04 (3H,s) --
Page 25
[148]
19 OAc – 3``` 2.15 (3H,s) --
20 OAc – 4``` 1.96 (3H,s) --
The 13
C NMR spectrum (300 MHz, DMSO d6 + CDCl3) gave 27
carbon signals which indicated the presence of 15 carbon signals due to the
flavonol skeleton. We found that both C-2 (158.02) and C-4 (179.66) were
down field shifted while C-3 (134.43) was up field shifted, demonstrating
glycosylation at C-3. The 134.43 confirmed that the C-3 was linked to the
glycosyl chain. In the 13
C NMR spectrum the C-6`` (glucose) was downfield
shifted at the c 68.81, inferring that the glycosylation of the glucose unit
by the rhamnopyranosyl took place on the 6``- hydroxyl.
Table – VIII
13C NMR Chemical shifts of the glycoside ppm from TMS
Assignments Chemical shift
C-2 158.02
C-3 134.43
C-4 179.66
C-5 162.00
C-6 99.90
C-7 165.00
Page 26
[149]
C-8 95.20
C-9 159.30
C-10 105.60
C-1` 122.44
C-2` 116.70
C-3` 145.60
C-4` 149.10
C-5` 117.10
C-6` 123.90
glu – C-1` 100.18
glu – C-2` 72.22
glu – C-3` 74.82
glu – C-4` 69.66
glu – C-5` 75.21
glu – C-6` 68.81
rham.-C-1` 103.10
C-2` 70.90
C-3` 71.20
C-4` 72.80
C-5` 70.50
C-6`-CH3 17.50
Page 27
[150]
Based on the facts and finding discussed above the glycoside could be
represented as quercetin -3-0- - L rhamnosyl – (1 6) - - D-
glucoside.
Mass spectrum of the glycoside:
The important fragmentation pattern obtained in the electron impact
mass spectrum of the glycoside is given below and further confirmed the
structure assigned to it.
The different species obtained during fragmentation are below and
were found to be in complete accord with the structure assigned to it.
Page 28
[151]
Mass : m/z 610 [M+], 560, 507, 448, 302, 301, 274,
273, 153, 152, 134, 132, 124.
The connectivities were determined and unambiguous assignments
were made for all of the protons and carbons.
Accordingly the structure of the flavonoid glycoside was stablished as
5,7,3`,4` tetrahydroxy 3 -0- - L rhamnosyl – (1 6) - - D- glucoside
(I).
(I)
Page 29
[152]
EXPERIMENTAL
Chromatography :-
TLC (Cellulose Plate) -
1. n BuOH – AcOH- H2O (4:1:3, v/v), Rf = 0.47
(Ammonia vapours)
2. n BuOH – Pyr - H2O (3:2:5, v/v), Rf = 0.43
(Ammonia vapours)
3. AcOH (30%) Rf= 0.52
4. MeOH-CHCl3 (1:9, v/v) Rf= 0.21
Test:-
The alc. solution of the compound 4-5 drops of - naphthol solution
was added on addition of conc. H2SO4 a violet ring was formed on boiling
with fehling solutions no reduction was observed and no violet colour, when
spot of the compound on paper was sprayed with AHP reagent and heated at
1000.
Page 30
[153]
Acid hydrolysis :
To be glycoside (75mg) dissolved in minimum amount of ethanol
(30ml) H2SO4 (7%, 15ml) was added and refluxed on a water bath three hrs.
The ethanol was removed by distilling the reaction mixture under reduced
pressure and the reaction mixture as diluted with water (100ml). This
aqueous solution was repeatedly shaken with ether; the etherial layer was
washed with distilled water, to remove mineral acid. It was dried over
sodium sulphate, crystallised from ethyl acetate-hexane mixture as brownish
yellow substance mp. 312-3140C is obtained.
Sugars:
The remaining aqueous solution was neutralised with barium
carbonate and the filtrate was concentrated under reduced pressure. This
gave positive Molisch‟s test and reduced fehling‟s solution. Upon cellulose
tlc plate gave a spot, Rf 0.52 (n BuOH, Pyr-H2O 4:1:5, v/v spray AHP)
identical with that of authentic sample of rhamnose and glucose respectively.
AGLYCONE :
Elemental analysis:
Found: C= 59.68% H= 3.30 %
Calculated C= 59.60 % H= 3.31 %
for C15H10O7
Page 31
[154]
Acetylation :
The aglycone (40mg) was dissolved in pyridine (5ml) and heated with
acetic anhydride (8 ml) on a water bath for 8 hrs. The reaction mixture was
poured over crushed ice. The residue upon crystallisation with methanol
yielded pure quercetin penta acetate (C25H20 O12) and mp 1980C.
Found: C= 58.77% H= 3.84%
Calculated: C= 58.59 % H= 3.90%
for C25H20O12
Molecular weight = 512 by mass spectroscopy
Acetyl group:
Found: C= 41.24%
Calculated C= 41.99 %
Methylation :
The aglycone (35 mg) was dissolved in acetone 3.0 ml and refluxed
with potassium carbonate (40mg) and dimethyl sulphate (3.0 ml) on a water
bath for twelve hrs. The reaction mixture was cooled and was poured into
ice cold water. The residue filtered and crystallised from methanol to yield
an methylated aglycone, mp. 1460C, molecular formula C20H20O7.
Page 32
[155]
Found: C = 64.50% H= 5.38%
Calculated C = 64.51 % H = 5.37%
for C2oH20O7
Percentage of methyl group - Found 20.17%
Calculated 20.16 %
KMnO4 oxidation of methyl ether of aglycone:
Methyl ether of the aglycone (20 mg) in acetone solution was refluxed
with KMnO4 (40 mg) on a water bath for five hrs. The reaction mixture was
cooled, dilute with water and the solvent was removed by distillation. A
solution of sodium bisulphite was added to remove the excess of magnese
dioxide formed. The solution was extracted with ether and the etherial
extract was shaken with aq. saturated solution of sodium bi-carbonate. This
solution was acidified with HCl and repeatedly extracted with ether. The
ether extract on concentration gave veratric acid, mp. 180o. It was further
identified by mp and co-chromatography (n-Butanol saturated with ammonia
spray – bromophenol blue, rf = 0.42 with an authentic sample of veratric
acid.
Methyl ether of aglycone oxidation
KMnO4
Veratric Acid
Page 33
[156]
Spectral studies:-
UV:
MeOH
max
: 258, 304 sh, 372,
+NaOMe : 248 sh, 320 d
+AlCl3 : 275, 304 sh, 333, 460
+AlCl3/HCl : 265, 301 sh, 360, 430
+Na OAc : 257 sh, 274, 330, 390
+ NaOAc/H3BO3 : 261, 301 sh, 390 nm.
IR:-
KBr
max : 3407, 3310, 1665.85, 1610.45, 1562,
1522, 1453;59, 1262. 29, 822.70 cm-1
1H NMR :
(CDCl3 300 MHz)
ppm :
: 6.17 (1H,d, J = 2.0 Hz , H-6)
: 6.37 (1H,d, J = 2.0 Hz, H-8)
: 6.87 (1H,d, J = 8.0 Hz, H-5`)
: 7.73 (1H,d, J = 2.0 Hz, H-2`)
: 7.62 (1H,dd, J = 2.0,7.5 Hz, H- 6`)
Page 34
[157]
13C
NMR :
(CDCl3+ DMSO d6 300 MHz)
ppm :
Assignments Chemical shift (ppm)
C-2 156.11
C-3 135.58
C-4 175.46
C-5 160.64
C-6 98.07
C-7 163.64
C-8 93.16
C-9 147.18
C-10 102.94
C-1` 119.91
C-2` 115.19
C-3` 144.61
C-4` 146.20
C-5` 114.84
C-6` 122.13
Mass :- 302 [M+], 301, 274, 273,
(70-ev; direct inlet m/z) 153, 152, 134, 132, 124,
Page 35
[158]
GLYCOSIDE :
Elemental analysis :
Found: C = 53.12% H= 4.92%
Calculated C = 53.11 % H = 4.91%
for C27H30O16
Per iodate oxidation :
The methylated glycoside (20mg) was dissolved in aq. ethanol (50%,
30 ml) and 10 ml of o.1 M sodium meta per iodate was added to it. A blank
experiment was similarly run. Both were kept at room temp. for 48 hrs. The
mole of per iodate consumed and mole of formic acid liberated were
calculated by the method of Hirst and Jones. It was observed that :
Moles of per iodate consumed = 3.06
Moles of formic acid liberated = 1.1
Mild hydrolysis:
The glycoside (20mg) was refluxed with 1% aqueous H2SO4 (4.0
ml) for 5 hrs. small aliquots were taken out from time to time from the
reaction mixture, neutralised with barium carbonate and tested for sugar.
Page 36
[159]
Rhamnose its appearance just after some time and glucose was detected after
one hour.
Permethylation and hydrolysis:
The permethylated glycoside (30mg) was hyrolysed with
2N-H2SO4
for four hrs. The hydrolysate was neutralised with barium
carbonate, filtered and concentrated in a rotary evaporator. This solution
when chromatographed over whatman No.-1 chromatographic paper using
quercetin 3 -0- - L rhamnosyl – (1 6) - - D- glucoside as
reference sugar revealed the presence of 3 -0- - L rhamnose and -
- D- glucose (B:E:W; 5:1:4, v/v, spray AHP).
Acetylation :
The glycoside (40 mg) was acetylated with acetic anhydride (8ml) and
pyridine (5 ml) on water bath at room temperature for 8 hrs.
The reaction mixture was poured over crushed ice with stirring and
left over night. The acetate obtained was filtered and washed with cold water
as colourless micro crystalline, solid mp 2040C and analysed for deca acetyl
group by the method of Weisenberger as described by Belcher and
Goldbert38
.
Page 37
[160]
Elemental analysis :
Found: C = 54.76% H= 4.87%
Calculated C = 54.75 % H = 4.85%
for C47H50O26
Percentage of Acetyl group:
Found : 41.75%
Calculated : 41.74 %
Spectral Studies :
1H NMR:
(DMSO + CDCl3 300 MHz)
: ppm : 7.82 (1H,d, J = 2.0 Hz , H-2`)
: 7.57 (1H,dd, J = 2.0, 7.5 Hz, H-6`)
: 6.85 (1H,d, J = 8.0 Hz, H-5`)
: 6.12 (1H,d, J = 2.4 Hz, H-6)
: 6.30 (1H,d, J = 2.0,Hz, H-8)
: 5.18 (1H,d, J = 7.6,Hz, H-1`` glucosyl)
: 4.38 (1H,d, J = 2.0,Hz, H-1``` rhamnosyl)
: 3.60 – 3.85 (4H,br,m, sugar protons)
: 0.90 (3H,br,m J = 6.3 Hz, rhamnose methyl)
Page 38
[161]
13 C NMR :
(DMSO + CDCl3 300 MHz)
: ppm
Assignment Chemical Shift
C-2 158.02
C-3 134.43
C-4 179.66
C-5 162.00
C-6 99.90
C-7 165.00
C-8 95.20
C-9 159.30
C-10 105.60
C- 1` 122.44
C-2` 116.70
C-3` 145.60
C-4` 149.10
C-5` 117.10
C-6` 123.90
Page 39
[162]
glu – C-1` 100.18
glu – C-2` 72.22
glu – C-3` 74.82
glu – C-4` 69.66
glu – C-5` 75.21
glu – C-6` 68.81
rham-C-1` 103.10
C-2` 70.90
C-3` 71.20
C-4` 72.80
C-5` 70.50
methyl C-6`-CH3 17.50
Mass : (m/z) : 610 [M+], 560, 507, 448, 302, 301,
274, 273,153, 152, 134, 132, 124.
Page 40
[163]
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